.TH std::move_backward 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::move_backward \- std::move_backward

.SH Synopsis
   template< class BidirIt1, class BidirIt2 >                   \fI(since C++11)\fP
   BidirIt2 move_backward( BidirIt1 first, BidirIt1 last,       (constexpr since C++20)
   BidirIt2 d_last );

   Moves the elements from the range [first, last), to another range ending at d_last.
   The elements are moved in reverse order (the last element is moved first), but their
   relative order is preserved.

   If d_last is within (first, last], the behavior is undefined. In this case,
   std::move may be used instead.

.SH Parameters

   first, last           -           the range of the elements to move
   d_last                -           end of the destination range
.SH Type requirements
   -
   BidirIt1, BidirIt2 must meet the requirements of LegacyBidirectionalIterator.

.SH Return value

   Iterator in the destination range, pointing at the last element moved.

.SH Complexity

   Exactly std::distance(first, last) move assignments.

.SH Possible implementation

   template<class BidirIt1, class BidirIt2>
   BidirIt2 move_backward(BidirIt1 first, BidirIt1 last, BidirIt2 d_last)
   {
       while (first != last)
           *(--d_last) = std::move(*(--last));

       return d_last;
   }

.SH Notes

   When moving overlapping ranges, std::move is appropriate when moving to the left
   (beginning of the destination range is outside the source range) while
   std::move_backward is appropriate when moving to the right (end of the destination
   range is outside the source range).

.SH Example


// Run this code

 #include <algorithm>
 #include <iostream>
 #include <iterator>
 #include <string>
 #include <string_view>
 #include <vector>

 using container = std::vector<std::string>;

 void print(std::string_view comment, const container& src, const container& dst = {})
 {
     auto prn = [](std::string_view name, const container& cont)
     {
         std::cout << name;
         for (const auto &s : cont)
             std::cout << (s.empty() ? "∙" : s.data()) << ' ';
         std::cout << '\\n';
     };
     std::cout << comment << '\\n';
     prn("src: ", src);
     if (dst.empty())
         return;
     prn("dst: ", dst);
 }

 int main()
 {
     container src{"foo", "bar", "baz"};
     container dst{"qux", "quux", "quuz", "corge"};
     print("Non-overlapping case; before move_backward:", src, dst);
     std::move_backward(src.begin(), src.end(), dst.end());
     print("After:", src, dst);

     src = {"snap", "crackle", "pop", "lock", "drop"};
     print("Overlapping case; before move_backward:", src);
     std::move_backward(src.begin(), std::next(src.begin(), 3), src.end());
     print("After:", src);
 }

.SH Output:

 Non-overlapping case; before move_backward:
 src: foo bar baz
 dst: qux quux quuz corge
 After:
 src: ∙ ∙ ∙
 dst: qux foo bar baz
 Overlapping case; before move_backward:
 src: snap crackle pop lock drop
 After:
 src: ∙ ∙ snap crackle pop

.SH See also

   move                  moves a range of elements to a new location
   \fI(C++11)\fP               \fI(function template)\fP
   ranges::move_backward moves a range of elements to a new location in backwards order
   (C++20)               (niebloid)
